The importance and need for continuous metabolites monitoring cannot be overemphasized. Most recent developments for in vivo monitoring devices have focused on miniaturization and the exploratory use of new functional materials. As most biosensors tend to drift and degrade over time, the development of a simple, dependable, on-demand, in situ (and possibly in vivo) self-calibration/self-diagnosis technique is a key obstacle for convenient, continuous monitoring with minimum intervention. The availability of this "weak link" would greatly improve the reliability and convenience of continuous in situ, in vivo monitoring technology. Biosensors featuring optical detection coupled with analyte sensitive fluorescent elements are particularly interesting. The objective of this proposal is to develop an integrated polymer fluidic microsystem for the continuous optical monitoring of lactate based on reversible hydrogen peroxide detection. This device features two novel design traits;(1) rejection of interferants through the use of photopatternable hydrophobic sensing elements and (2) an in situ self- calibration/self-diagnosis capability. Biosensors which utilize oxidase enzymes as biorecognition elements are inherently dependent on dissolved oxygen. Specific manipulation of this oxygen dependence in the sensor element microenvironment allows for not only in situ calibration for baseline checking, but it also provides a means to increase sensitivity through on- chip generation of oxygen. Importantly, the proposed microsystem with integrated calibrator, biofunctional film, and sensing element module establishes the calibrating and diagnostic microenvironment internally, minimizing the need for externally coupled bulky reservoirs and fluidic systems for continuous monitoring. Innovative functionalities of the integrated microsystem include: (1) rejection of interferants by the sensing element matrix material to minimize signal crosstalk, (2) one-point in situ self- calibration (zero-value calibration), and (3) increased sensitivity and minimum signal fluctuation through background oxygen concentration control. PUBLIC HEALTH RELEVANCE: The objective of this proposal is to develop an integrated self-calibrating/self-diagnosing optofluidic sensor system for the continuous measurement of lactate levels. A major feature of this system is the ability to manipulate oxygen levels in the sensor microenvironment to allow for both in situ device calibration and sensitivity enhancement. The device is designed to be amenable to the development of intelligent, autonomous sensors which may be applied to various metabolite monitoring scenarios including disease diagnosis and monitoring of patient or environment.